Vacuum pump

Abstract

A vacuum pump for rotary driving a rotor by a motor to perform vacuum pumping, wherein a motor rotor of the motor includes a yoke fixed to a shaft of the rotor, and a permanent magnet held at the yoke, and the yoke includes a holding portion provided apart from the shaft and configured to hold the permanent magnet, and a pair of fitting portions provided respectively at both ends of the holding portion in an axial direction and bonded to the shaft by fitting, and a radial thickness dimension of each fitting portion is set less than that of the holding portion.

What is claimed is: 
     
       1. A vacuum pump for rotary driving a rotor by a motor to perform vacuum pumping, wherein
 a motor rotor of the motor includes
 a yoke fixed to a shaft of the rotor, and 
 a permanent magnet held at the yoke, and 
 
 the yoke includes
 a holding portion provided radially apart from the shaft so as to define a space therebetween in a radial direction, and the holding portion configured to hold the permanent magnet radially outward from the holding portion, and 
 a pair of fitting portions provided respectively at both ends of the holding portion in an axial direction and bonded to the shaft by fitting, and 
 
 a radial thickness dimension of each fitting portion is set less than that of the holding portion. 
 
     
     
       2. The vacuum pump according to  claim 1 , wherein
 the fitting between each fitting portion and the shaft is tight-fitting. 
 
     
     
       3. The vacuum pump according to  claim 1 , wherein
 one of a surface of each fitting portion facing the shaft or a surface of the shaft facing each fitting portion is provided with a raised portion, and 
 the yoke and the shaft are bonded together at the raised portion. 
 
     
     
       4. The vacuum pump according to  claim 1 , wherein
 an axial width dimension of a bonded region of each fitting portion is set equal to or less than 10% of an axial width dimension of the yoke. 
 
     
     
       5. The vacuum pump according to  claim 1 , wherein
 the radial thickness dimension of each fitting portion is set equal to or less than 10% of an outer diameter dimension of the yoke.